The research of electromagnetic and thermoelectric processes in the AC and DC graphitization furnaces

Authors:

D.S. Yarymbash, Cand. Sci. (Tech.), Associate Professor, Zaporizhzhya National Technical University, Senior Lecturer of the Department of Electricity Supply of Industrial Enterprises, Zaporizhzhya, Ukraine.

Abstract:

Purpose. The investigation of regimes, 3D modeling and finite element method calculation of conjugate electromagnetic, electrothermal, heat and mass transfer processes of graphitization, the distribution of current density and power heating density at AC and DC graphitization, which are taken into account the constructions of graphitization furnace, core and packages of electric buses, the temperature dependence of electro, thermal and mass transfer properties.

Methodology. Numerical modeling of the conjugate three-dimensional electromagnetic and heat fields in the Acheson graphitization furnaces and electrode blanks by finite element method (FEM), the theory of electromagnetic fields, heat and mass transfer.

Findings. The theoretical research and modeling of electromagnetic and thermoelectric processes by numerical finite element method realization of the generalized three-dimensional models of DC and AC graphitization are proposed. The features of electromagnetic, electrothermal and heat-mass transfer processes in the graphitization furnace, core, and side bus packages of furnace loops are taken into account. It was established by researches that the increase of AC graphitization specific capacity in the end areas of blanks are achieved by surface effect in the core and of external surface effect of the side bus packages. It will allow to align the temperature distribution in the electrode blanks, to decrease the temperature differences, and to provide the higher level of electrode quality as compared with DC graphitization.

Originality. The character and laws of the distribution of current density and specific electrical losses in the core and electrode blanks during DC and AC graphitization, and their quantitative differences in the main and end areas of the core are determined.

Practical value. The three-step mode of the graphitization power input by the core temperature criteria is substantiated. The first phase is the DC until mean core temperature 1000°C, the second phase is the AC heating from temperature 1000 to 3000°C, the third phase is the ending phase of DC graphitization. This will reduce electricity consumption on the reactive power compensation on 70–75% during the campaign graphitization and energy consumption per ton of finished product on 4,2–4,5%. The developed technological approaches and regimes can be used in mining and metals production sector and related industries.

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